Google Code-in

Currently, most of the tests for the merger are run under Python. The valgrind tests for identifying memory leaks and errors can only run against tests in the C code. We need to replicate the python tests as C tests. This will ensure that these code-paths are scanned with valgrind for leaks when ninja test is run (and when the CI test suite is executed). Look at the tests being run in https://github.com/fedora-modularity/libmodulemd/blob/master/modulemd/tests/ModulemdTests/merger.py#L69 and copy them into https://github.com/fedora-modularity/libmodulemd/blob/master/modulemd/tests/test-modulemd-merger.c